Chicago Boys
by littlespider
Summary: Halstead and Mouse will always be the most unlikely of friends, the best of brothers. Exploring their friendship from their army days through Season 3. Rated for mentions of drug use and swearing.
1. Brothers in Arms

I am so happy that the new season of Chicago PD is finally here! I've found myself hit with major Halstead/Mouse bromance feels for the past week or so, which is where this fic came into being.

It's mainly going to be me recording my head-canon for this friendship, but there will be a few episode tags and AUs, so if you're into that, read on!

Disclaimer: Chicago PD belongs to NBC and the magnificent Dick Wolf.

* * *

" _Halstead!" Something - someone? - pounded on his chest, the dull thud echoing through his body. "Come on you bastard, open your eyes!"_

 _Well, since he'd asked so politely… Jay forced his eyelids open slowly and regretted it almost immediately as his already dry eyes were assaulted by thick, irritating smoke. He coughed harshly and blinked, trying to bring the face that hovered just in front of his own into focus. Finally succeeding, he found a pair of intense pale blue eyes staring at him out of a face covered in soot and blood._

 _Mouse cracked a smile. "Hey, hey, that's good. Ok, man, hold tight. We've gotta go."_

* * *

Greg Gerwitz, aka Mouse. Tell any one of his high school classmates that the rather eccentric tech geek would end up an Army Ranger and they might have laughed in your face. Gerwitz, go to war? Not on your life.

Jay Halstead had thought much the same when he first met Mouse in training, a skinny pale kid who looked like he'd never voluntarily done physical activity in his life. But Mouse surprised everyone, pushing through training and graduating at the top of his class. When he and Jay were assigned to the same unit shipping out, Halstead couldn't have been more pleased.

And thank god for chance meetings because Mouse Gerwitz ended up saving Halstead's life. Multiple times.

The first time was so routine that it didn't even occur to Halstead until days later. They were on foot patrol when they came under fire. Mouse, the unit's comm specialist, took out a hadji just as he turned his gun on Halstead. The man's body shuddered under the impact of Mouse's bullets, the gun slipping from his grip and his own fire striking the dusty street.

Instead of saying thank you, a week later Halstead got a chance to return the favor. When Mouse mentioned it that night in their barracks, Halstead slapped him on the back and said they were even.

Facing down death next to each other every day bonded the two men fast. They were two boys from Chicago feeling very far from home and the war made them brothers. Halstead was slightly older, more serious, and always ready to stand up for Mouse when the others got tired of his quirks. Mouse was brilliant, sometimes to a fault, full of energy, and ready for anything, especially if it was Halstead's suggestion. Together, they were unstoppable.

It's towards the end of their second tour that they have the incident with the convoy.

The mission was to press forward and join the men fighting on the front lines. It had been a relatively small convoy, just three humvees, with the hope that they would attract less attention. Mouse and Halstead took the lead humvee.

Miles went by with relatively little incident until they hit the IED.

Halstead didn't remember much about the actual detonation. They had been following the road, if you could call it that,a crumbling hill to one side and a dip down the other. It seemed so sudden; they rolled over a slight divot in the ground and a violent jolt had Halstead smashing his head against the humvee's metal interior. When he came to, the humvee was upside down and Mouse was up close in his face, trying to rouse him.

Thompson, their gunner, was dead.

Halstead kept fading in and out, but the next thing he knew Mouse had somehow managed to get them out of their burning vehicle, though things weren't much better out in the open. The rest of the convoy was taking heavy fire from up on the hill and Halstead managed to rouse himself just enough to watch as the third humvee was absolutely demolished by an RPG.

Mouse maneuvered Halstead, who was hammered by a serious head injury and a broken leg, across the street and into the ditch, pressing the taller man's head down into the sand with an order to "Stay here!" before he took off himself towards the remaining humvee. Disoriented, Halstead remained down as ordered until Mouse returned with the three men from the second humvee, the only remaining members of their unit.

It took two hours of staying low and patiently picking off their attackers before the boys of the 75th regiment could finally stop and take a breath. Deciding the demolished humvees drew too much attention, the unit proceeded further down the dip, staying parallel to the road, going just so far as to not be seen from the road but close enough to see any approaching rescue. It took both Mouse and Mackie to move Halstead, who was trying his best not to pass out from pain, but they managed.

That was when Halstead noticed the growing stain of red on Mouse's torso that spread outwards and down on leg of his fatigues.

Closer examination found that a twisted piece of metal from their mutilated humvee had pierced Mouse's side, just above his hip. The bleeding was steady, but not yet life threatening if they got help in the next couple of hours. They opted to leave the metal in.

Besides, Mouse was the only one of them with the know-how to get their comms back up and running. Garcia and Hollinsworth took a trip back to the humvee to retrieve the portal backup radio and Mackie packed gauze around the protruding metal before splinting Halstead's leg as best he could.

Regardless of the fact that he was bleeding out, Mouse's shaking fingers were as nimble as ever. In just 20 minutes he had the comms back on and in another five he'd radioed in to base and received confirmation that an extraction team was on their way.

That was the day Halstead decided that he would take shoot outs or explosions over waiting any time. Waiting was hell. Waiting meant watching Mouse go from alert to slouched over and pale, his ever fidgety fingers still managing to tap out a light beat against his pant leg. They were all still tense and on edge, never completely convinced that they wouldn't be attacked again before the extraction team arrived. With his head wound, Halstead kept fading in and out, but even he was aware that they were low on med supplies, low on water, and low on time.

When evac finally got there, the two Chicago boys had passed out, slumped next to each other on the red-stained sand.

Halstead remained unconscious for almost three days while Mouse underwent a series of surgeries and blood transfusions. When he woke up, they were back stateside. Doctors informed Halstead that he was lucky; he'd suffered no apparent brain injury and his leg would be back in working order after a couple of months of physical therapy. He would recover enough to serve out the remainder of his enlistment.

Mouse came around a couple of days later and although he was still weak and a little pale, Jay was just relieved to see him alive.

Three months later, Halstead was on a military transport back to Afghanistan. But this time he was on his own. Although Jay never actually learned why, in the few days that he had been out from his head wound, Mouse had been medically discharged.


	2. Adjustment Period

Thank you all so much for the kind responses to the first chapter! To answer the most common question: Yes! I will be continuing this and based on my current outline, it's going to be a long one!

Just a quick warning for this chapter: There's a bit of cussing to accurately portray man-angst. Enjoy!

* * *

 _Mouse cracked a smile. "Hey, hey, that's good. Ok, man, hold tight. We've gotta go."_

 _Go? Before Halstead could reorient himself, Mouse was grabbing at his arms and hauling him up and forward. The movement sent a brilliant flash of hot pain through Halstead's left leg and he shoved his friend away roughly, landing on his backside in an uncoordinated heap._

" _Fuck!" Squinting at his leg through the increasingly thick smoke, Halstead thought he could see the bright white of bone poking out through a tear in the leg of his fatigues. With any luck, he was hallucinating. "What-"_

" _Uh, yeah, it's broken," Mouse confirmed, with all of his usual lack of tact as he coughed in the smoke.. "But you're gonna hafta suck it up, man, 'cause we're sittin' on our heads and this tin can is on fire."_

 _Right, that would explain the smoke and why the heat was getting unbearable. Halstead had no desire to go by fire. He'd seen too many burn victims: civilian victims in suicide bombings, fellow soldiers in the aftermath of an RPG. Most who met with an IED didn't live long enough to burn. No, Halstead would not be going by fire._

 _Even still, when Mouse somehow managed to get behind Halstead and haul the taller man upright, it only took one step before Halstead found himself fading into oblivion._

* * *

It was Mouse who picked Jay up from the airport the day he finally returned to Chicago a free man. It was only fair, he reasoned, since Mouse had been staying at his apartment until he got his post-army life together. No point in letting the place sit empty while Jay was overseas.

Besides, Will was off doing his residency in New York and their father... Well, Jay hoped the next time he was forced to interact with his father was at the old bastard's funeral.

"Hey, man." Mouse didn't do some big, sappy 'Welcome Home,' which Jay appreciated. Instead he just launched right into one of his usual high speed, semi one sided conversations. He filled Jay in on his job search and how the plants at his apartment were doing and how he wouldn't believe that they'd taken out the old convenience store on the corner of their block.

Jay loved the normalcy of it all.

That first weekend back, Jay felt like he was living on cloud nine. He was finally at home, sleeping in his own bed, and without the threat of an upcoming tour looming over him. He stopped in at all his old neighborhood haunts and was welcomed back with open arms, the prodigal son, the local hero. The men respected him and the women wanted to sleep with him, and he honestly couldn't remember ever loving Chicago so much.

And then, as it always does, Monday rolled around and dumped a big old bucket of ice water on Jay's victory lap.

It was peanut butter, of all things, that set him off. He'd accompanied Mouse to the grocery store, though they agreed to divide and conquer and carry their own baskets (sharing a cart just felt too domestic). Mouse was getting the bread. Jay was in charge of jelly and peanut butter.

Jelly had been easy enough. He found his old favorite sitting right on the top shelf where it should be, Welch's Grape. But then he scooted over to grab some peanut butter and was struck with sudden confusion. Since when were there this many kinds of peanut butter? And he wasn't just talking smooth or chunky, Skippy or Jif.

There was no fat, low fat, no added sugar, all natural. There was also organic, just in case all natural wasn't natural enough for you. There was peanut butter mixed with honey, peanut butter in 100 calorie snack packs.

Jay didn't even want to know what the hell almond butter was. Seriously, what happened to don't mess with the classics?

"Jay?"

Even though he knew he was safe, in Chicago, in the grocery store, in the middle of what was apparently the world's largest peanut butter ilse, Jay jumped. Mouse, standing there with his basket full of bread, eggs, milk, and fresh produce, didn't seem phased by his friend's overreaction. While Jay stood suddenly and inexplicably tense, as though waiting to be reprimanded for taking so long with the one item he'd been assigned, Mouse seemed to know, as always, what to say.

Turning to scan the long shelf of different spreads, Mouse snorted. "God bless America, huh? Only place in the world where they think we need a fuckin' million different kinds of peanut mush."

Jay forced a laugh and, after Mouse snagged a jar from the shelf directly in front of them (creamy Skippy, Jay's favorite), followed his friend toward check out.

Things for Jay went downhill from there. He started picking up on more and more little changes in the city since he'd last been home, from the missing graffiti thanks to the Mayor's new task force to the mom and pop businesses that were closing on every corner. He also wasn't sleeping, though not for lack of trying. Someone needed to tell his brain that he could really use the sleep; damn nightmares.

And worst of all, he was still jumpy as all hell. A kid could screech a laugh and he'd be back in the sand, and a car backfiring had him taking cover behind the nearest building, waiting for the bullets to start flying.

Jay assumed this was what going mad felt like.

Drinking made it better, or at least that's what Jay told himself. It at least took the edge off, dulled his senses enough that he wasn't walking around in a state of hypervigilance all the time, constantly ready for fight or flight. So, logically, the solution was to just be drinking all the time.

The key was drinking, but not _drunk_ , all the time. Drunk meant out of control, which was just as bad as hyper aware (Jay and Mouse learned this the hard way the one night Mouse was unlucky enough to surprise a completely wasted Jay when he came home from work). 'Course, he couldn't drink at the bar all day because then people would know that he wasn't a hero, that he'd come home broken. So Jay sat in the semidarkness of his living room nursing room temperature beers until a more acceptable evening hour to wander over to his local Irish pub.

Mouse took this all in stride, for the most part. After that one incident landed Mouse with a black eye and split lip that had been hell to explain to his boss, he mainly stayed out of Jay's way, but always made sure he ate and had somebody there to listen, if he decided he finally wanted to talk. He often waited up at night until Jay came stumbling back into the apartment, rambling about how he was sorry he'd had to shoot that one suicide bomber, a beautiful girl in her early 20s. Mouse would manhandle Jay into bed with a big glass of water and make sure he took off his shoes.

But everybody has a line and Mouse finally found his the night Jay brought home Amber.

He'd picked up Amber, or whatever her name was, at one of the three bars he'd visited that night. More like, she had attached herself to him and he hadn't been able to shake her off. Sober Jay wouldn't have touched that girl with a ten foot pole. She had a nice enough figure and had thick black hair, but her nails were littered with nicotine stains and she was missing several teeth. Not to mention the poorly done tattoo of a girl riding a bottle on the back of her dimpled thigh, or the fact that she smelled like week-old cheese burgers.

Luckily for Jay, Mouse was home when they came tumbling through the front door, Amber fully latched onto Jay's face. Mouse was on his feet in a second, expertly detaching the two less than sober strangers and sending the girl away with a few bucks for cab fare. For his part, Jay was so out of it that he didn't put up much of a fight even when Mouse stripped him down to his boxer shorts, forced him a glass of water down in his throat, and then tucked him into bed.

When Jay woke up in the morning, he barely remembered getting home, let alone whatever acts of kindness Mouse had performed. So when he wandered into the kitchen, he didn't spare the other man a glance where he stood, pulling on his jacket by the door. Instead, Jay made a beeline for the refrigerator, only to find that the beer he had purchased just yesterday was mysteriously missing.

Jay slammed the refrigerator door shut in frustration, making Mouse jump. Two steps and he was standing right up close in his friend's face.

"What happened to the six pack that was in the fridge?" Jay asked, point blank.

Mouse held his stare for all of two seconds before allowing his gaze to slide to the ground. "Oh, I, uh, I dumped it."

"You did what?" Jay demanded, unconsciously drawing himself up to his full, intimidating height, and Jay Halstead was in no way a small man.

"I said I dumped it." Mouse looked back up challengingly, finally finding his resolve. "This has gotta stop, man. I tried givin' you space, let you try and work your shit out, but I'm done. I'm not going to let you keep doin' this to yourself."

Jay snorted, his hands clenching into fists as he brought his arms up to cross his chest. "Yeah, right, 'cause you're the poster boy for having your life together."

Mouse's expression tightened a little, hurt reflecting in his pale blue eyes. "Yeah, well, at least I'm tryin'. Look, I, uh, I left some numbers on the counter for you. One's this army doc-"

"I don't need a shrink," Halstead ground out angrily, stalking back towards the kitchen.

"Ok, maybe you don't," Mouse said placatingly, raising his hands in front of him. "But her number's there and so is the number for your sergeant at the district. He called the other day, wonderin' if you'd want to come back to work."

At the mention of his CPD sergeant, Jay froze, his back still to Mouse and the door. When he didn't say anything after a minute of silence, Mouse sighed and opened the door. "Just thought you might wanna know."

And then he was gone, off to work. For what it was worth, Halstead did pick up the scrap of paper Mouse had scribbled the numbers on, folded it up, and stuck it in his wallet. But he wasn't there when Mouse got home.

Mouse found Jay in a booth towards the back of the bar, where he'd somehow managed to convince the bartender to leave him an entire bottle of whiskey. Mouse slid into the seat opposite Jay, his leg shaking with nervous energy under the table. "Hey."

Jay glared at him over the top of his glass. "What do you want?"

"I just, I, uh," Mouse's fidgeting increased under the strength of Halstead's gaze. "Why don't you and I take a walk, huh? Get some fresh air?"

Jay snorted, reaching out to grab the bottle by the neck in case Mouse tried to take it away. "Yeah, I don't think so. How 'bout you go fuck yourself?"

If Jay hadn't been way passed buzzed and making his way towards stupid drunk, he might have seen the violent way Mouse flinched at his rough words. But the smaller man persevered.

"I'm serious, man. Let's get out of here."

Again, if Jay wasn't already completely gone he might after felt the little warning snap inside of himself, the sudden rush of heat rising from his gut. Instead he shot to his feet, swaying slightly, and leaned over the table to get in Mouse's face. "Alright, you wanna get out of here? Ok. Let's go."

Jay slapped a stack of bills down on the table, grabbed his jacket, and led Mouse out of the dimly lit bar through the side exit. They had just barely stepped out into the trash-littered alley when Jay whirled, landing a solid right hook on Mouse's temple. The smaller man grunted under the impact, staggering back into the building wall. Jay didn't give him a chance to recover, slamming another fist into Mouse's torso.

Despite his slender frame, Mouse wasn't the kind of guy you could just knock over. Dodging away from a third hit, Mouse launched himself forward and pushed Jay, hard, trying to get some space between them and the wall. Jay's first found its mark again, this time on his jaw. Undeterred, Mouse ducked a particularly wild swing from Jay's left and and finally succeeded in getting a hold of Jay's shoulders. Just a second later he had Jay in a chokehold, though the larger man's size made it difficult to subdue him.

"Jay!" Mouse gasped, trying his damndest to hang on to the thrashing man beneath him. "Stop!"

The sounds of their scuffle attracted the attention of a local foot patrol. The two baby-faced policemen shown their flashlights at the two former soldiers, looking apprehensive. "Police! Step away from each other!"

"Hey, hey, man, we're cool," Mouse rushed to assure the officers, somehow managing to crack a smile even with blood running down his face where Jay's knuckle had split his skin. Under his choke hold, Jay had sunk to his knees in the grimy alleyway. "My brother here just got a little excited. He's just back from the war and all… But we're all cool now, guys."

At the mention of Jay's service, the two officers exchanged a look. "He's your brother?"

"Yessir," Mouse replied, his voice deceptively calm. He could feel Jay's muscles starting to go slack underneath him as his choke hold finally took effect, restricting Jay's airway. Give it another thirty seconds and he had Jay down. "I'm gonna take him straight home."

The policemen paused again, silently checking in with each other. Finally one of them nodded. "Alright, but you better be going home. We don't wanna see your faces again tonight or hear about you from our commander in the morning."

"Understood, sir," Mouse replied, loosening his grip slightly so Jay didn't pass out. Seemingly satisfied, the two cops nodded once more and moved further up the street, glancing back occasionally. Once they were out of view, Mouse released Jay entirely with a grunt of effort, though he didn't move when Jay sagged back against him, coughing and sucking in air.

"You-," Jay cut himself off with a raspy cough. "You shouldn't lie to police."

"I didn't," Mouse stated matter of factly, positioning himself under one of Jay's arms and hauling them both to their feet. "Come on, brother, let's get you home."

Jay woke up the next morning to one of the worst hangovers he'd ever experienced, but that wasn't the only reason he felt bad. He found Mouse still asleep on the couch, way past when he normally left for work. A bag of not-so frozen peas was slowly melting on the coffee table and the whole right side of Mouse's face was one big swollen bruise. Dried blood was caked in the corner of his mouth and along a slight split at his temple.

For the first time in months, Jay bypassed the refrigerator to turn on the coffee maker. After having a cup and checking that Mouse was still breathing and didn't have a concussion, Jay fished the paper with Mouse's scribbles out of his wallet and picked up the phone.

* * *

Making that call turned out to be one of the best decisions Jay had ever made. The army shrink Mouse had referred him to was younger than he'd thought and she'd served overseas herself far longer than Jay had. Talking to her was easy and he found himself actually looking forward to each session.

It took almost two months of sessions before Jay got up the courage to call his old police sergeant back. Luckily for him, there was still an opening at the district and he was informed he'd be welcomed back whenever he was ready. When he told Mouse that night over dinner, the smaller man couldn't even manage to look surprised.

"Told you so," he shrugged, laughing when Jay flicked rice at him in mock annoyance.

That was another thing that had changed. He wasn't sure at what point Mouse had ceased to be just his friend and had become his keeper, but now Jay was at least making an effort to make sure Mouse knew how much he appreciated all his friend had done for him since he'd been back stateside. They made a point to have dinner together when their schedules permitted and that was the only time Jay allowed himself to drink, when he and Mouse were relaxing in the evenings, each with a beer at their side.

Of course, Mouse wasn't actually around a lot and when Jay did see him, he looked practically dead on his feet. He'd been working as a loader at a local warehouse and he told Jay that he was taking all the extra shifts he could get so he could save up to get a car or, better yet, a place of his own.

"Not that I don't appreciate the couch and everything," Mouse said one evening, as he washed their dishes and Jay dried. "It's just been a while since I've had my own space, ya know?"

Jay just nodded and took Mouse's word for it. He didn't have any reason not to.

* * *

"Halstead, you have a minute?"

Jay was on his way out when the watch commander called him into his office. He saw his current sergeant in the room as well and couldn't help the tingling of nerves in the tips of his fingers. Was something wrong? He'd been back on the job about six months and, as far as he was concerned, everything was going remarkably well. He'd taken a few weeks to get back into the rhythm of things, but once he settled in he quickly reclaimed his title of most productive patrolman and was even loaned out to help homicide with some of their investigations.

Still, when the commander and your sergeant want to see you, it's normally not good news.

"Sir?" Jay asked, standing ramrod straight in front of the commander's desk and trying to keep his apprehension from showing on his face.

"Take it easy, Patrolman, this isn't a reprimand." The commander chuckled, exchanging a look with Jay's sergeant. "I just wanted to say nice job on the Carmichael case."

Carmichael was a murdering wackjob who had a serious fetish for closeted gay men. He liked to seduce them, kill them, and then have his way with them. Jay had found himself going undercover in one of the Chicago's more ritzy gay clubs to get close to the killer and, thankfully, the sting had gone off without a hitch.

Surprised, Halstead blinked. "Thank you sir."

"There's something else," the commander said, leaning back in his chair. "Antonio Dawson stopped by today. Apparently there's an opening for a new detective in Intelligence and Sergeant Voight was impressed enough with your handling of the Carmichael case that he's convinced himself you're the only man for the job. Congratulations."

Jay couldn't get home soon enough. He pushed it through traffic as fast as he dared, then raced up the stairs of his creaky old apartment building. He kept fumbling with his keys in his excitement and when he finally got the door open, he slammed it against the wall accidentally.

"Hey, get your shoes on, man, we're going out tonight. Guess who got promoted!" Jay's proud announcement was met with silence. "Mouse?"

The pillow and blanket on the couch had been folded and arranged neatly, the rucksack missing from its normal hiding place just under the coffee table.

Mouse was gone.


	3. Breakdown

I am being bombarded with so many ideas for this fic right now, it's kind of crazy. Thanks again for all the kind comments!

* * *

The night Halstead was promoted to detective, the night he came home to find Mouse gone and all traces of him removed from the apartment, he drove the streets until the early hours of the morning looking for his friend. He check local haunts and Mouse's old neighborhood, but with no luck. All of his calls to Mouse's cell went straight to voicemail. Where ever he had gone, apparently Mouse didn't want Halstead to know.

Jay didn't bother filing a missing person's report. He knew there was very little the cops could do for him, what with Mouse being a full grown adult and the two men not being actual brothers, despite what Mouse said.

That didn't stop the nagging feeling that something was wrong. Mouse wouldn't have just taken off like that, not under normal circumstances, not when Jay was finally getting his life together. Besides, he didn't have anywhere else to go. Mouse's parents had died in a tragic car accident when Mouse was still in high school and his grandmother, who he'd lived with after the accident, passed away during the boys' first tour.

Halstead at least had Will, although his brother was a bit of a flake. As far as Jay knew, Mouse didn't have anybody but him.

Fear for his friend kept him searching, as did the guilt. Halstead couldn't help but feel like he'd been taking Mouse for granted since he got home, forcing his friend to put up with all his shit while Mouse probably had enough going on in his own head.

A week after Mouse went missing, his cell number was disconnected. Jay started making weekly rounds to local veterans' centers and homeless shelters with a recent picture of Mouse, calling to check in if he couldn't get off shift. He even pulled aside some of the patrolmen in his district and asked them to keep a look out for a man matching Mouse's description.

It wasn't as though Mouse had just evaporated. Somebody had to know something.

The only other place Jay could think to look was at the warehouse where Mouse worked, only to realize that he didn't actually know which warehouse that was. So he took a day off work to stop at all the warehouses with major loading facilities that Mouse could have gotten to without a car from Jay's apartment. He showed Mouse's picture around and after a whole day of "Never seen that guy in my life. He toldya he worked here?" Halstead was forced to face the possibility that Mouse had been lying to him the whole time.

But if he hadn't been working, where had Mouse gone everyday? As a police officer, Jay could think of several possible explanations, none of which were legal or ended well for his friend.

So imagine Halstead's surprise when, six months later, Intelligence stormed the house of a guy suspected of dealing explosives to various shady players to find no suspect and Mouse the only person in the building.

The Intelligence unit breached the stash house in tight formation, splitting up into two-man search parties once the entryway was cleared. Halstead followed Detective Antonio Dawson towards the back of the house, focus tight and long gun at the ready. Antonio had been one of Jay's training officers back when he'd first joined the CPD and he considered the older man among one of a very small number of people he could completely trust. So when the dark haired detective waved him silently into the room, Jay was quick to follow.

The room was sparsely furnished with a ratty looking couch positioned crookedly in the center of the room and a rickety table pushed up against the back wall, an ancient looking computer monitor perched carefully on top. Halstead could just make out a man in a hoodie sitting in front of the computer, typing away in the dim light.

Antonio stepped forward cautiously, gun raised. "CPD. Put your hands up and get on your feet."

The man's shoulders stiffened, his fingers stilling on the keyboard. Slowly, he raised his hands until they were parallel with his head, but remained sitting. Exchanging a tense look with Antonio, Halstead lowered his gun, stepping around to the side of the chair to yank the man to his feet. "You heard him! We don't have all- son of a bitch."

The dark hood fell back as Jay grabbed the man and Halstead suddenly found himself staring at a very pale and very stoned Greg Gerwitz.

Before Halstead himself even knew what he was doing, he'd off and punched Mouse right in the face. He felt his friend's nose give slightly under his fist. Mouse gave a strangled cry of pain and immediately reached up to cup his face in an attempt to stem the blood that rapidly spurted from his nose.

"The hell, Mouse?" Jay yelled, months of concern and fear coming out as anger. "I've been looking everywhere and I find you sitting here in a house full of explosives? I swear to god-"

"Woah, Halstead, back off!" Antonio barked, pushing the other detective away from the now bleeding Mouse, who he then grabbed by the bicep. "Are you saying you know this idiot?"

"Yeah, or at least I thought I did." Jay ground out, breathing heavily from his outburst.

Antonio seemed to pick up on the tone of Halstead's voice and gave the younger detective a long look. Then, with a sigh, he pried Mouse's hands from his face to cuff them behind his back. "Ok, then you get a crack at him in the box. For now Voight'll want to see him, preferably in one piece."

* * *

Voight wandered into the glass viewing room, where Antonio and Halstead were deep in heated conversation. "How's it going?"

"Not good, boss." Antonio shook his head. "I've been in there with him for almost an hour and-"

"He's not gonna talk," Halstead cut in, shaking his head in resigned frustration. "He might be stoned out of his mind, but he's been trained for interrogations. He's not gonna give you anything."

Voight was silent for a moment, his whole face furrowed in thought. Then he looked up at his detectives. "Ok, here's what we're gonna do. Antonio, take O and start looking for another angle. Go back over what we picked up at the house, see if we missed anything. Halstead, you get in the box and get your friend talking."

Halstead scoffed before he could stop himself. "I don't think he'll want to talk to me either, Sarge."

"That's funny, 'cause that was an order, not a request." Voight responded, leveling a glare at the young detective that would have seasoned criminals shaking in their boots. "I'm sure you'll think of something."

Jay might have been the newest member of Intelligence, but he was smart enough to know that ignoring a direct order from Hank Voight meant a quick trip to a lifetime of night patrol. Glancing briefly at Antonio, Halstead shouldered his way past the two older men and straight through the door of the interrogation room.

Mouse was sitting in the dimly lit interrogation room, leaning forward against the battered table. Antonio had removed his cuffs at the start of the interrogation and Mouse was tapping a steady rhythm on the tabletop, one leg jiggling under his seat. Jay stood by the door, taking in the sight of his friend.

In the six months that Mouse had been missing his hair had grown out from its short military cut, giving him a shaggy, disheveled look completed by several days worth of scruff. His nose had finally stopped bleeding, though it was still red and swollen. His cheekbones stood out prominently on his pale face and his eyes, focused down on the table and his tapping fingers, were wide and bloodshot, his pupils blown wide open. If Jay looked closely, he could see a trickle of sweat roll down past the collar of Mouse's well worn, yet relatively clean sweater.

Taking a deep breath to clear his head, Jay took a seat across from Mouse. Better get on with it. "Hey, uh, sorry about the nose."

Mouse's only acknowledgment was a slight flicker of his gaze up towards Halstead's face before returning his focus to the table top.

Halstead gritted his teeth and resisted the urge to glance back at the mirror, where he knew Voight was watching. "Come on man, you don't have to do that with me. I know all the tricks, remember? You go someplace else in your head, get in a rhythm, find something else to focus on. That's what kept Hollinsworth alive, right?"

Mouse's tapping paused momentarily before it started back up. Finally snapping, Jay shot his hand out, grabbing Mouse's wrist to stop that damn tapping. "Damn it Mouse, just stop and listen to me for second! You're in a real bind ok? We found you in a house with the same explosives that were used to kill a family of four last week. The boys were twins, nine years old."

 _That_ got to Mouse, just as Halstead hoped it would. His bloodshot eyes bored into Halstead's. "I didn't have anything to do with that, man."

"I know you didn't," Halstead assured him, thankful that he'd finally gotten his friend talking. "But I can't guarantee the DA's gonna see it that way. As far as he's going to be concerned, you were in possession of the murder weapon."

"Nah, man," Mouse insisted, leaning back in his chair as Jay released his wrist. "I was just crashin' there for the night. I didn't murder any little kids."

"I know," Halstead repeated, keeping his voice low and calm. "But I think you know who did. All you gotta do is give us a name."

Mouse hesitated, already shaking his head, his leg moving a million miles a minute. "He'll know it was me, man. He probably already knows I got pinched..."

"Mouse, let me worry about that." Halstead assured his friend, leaning across the table and closer to his friend. "You trust me, right?"

Jay waited, heart pounding oddly, for the smaller man's response. Once upon a time, in the not so distant past, they both would have responded instantly that they trusted each other with their lives. Eventually, Mouse took a deep breath and slowly nodded.

"Good. You help us out, we protect you."

* * *

Mouse's tip paid off. Intelligence found their explosives dealer making a sale at the docks, right where Mouse said he would be. Patrol also stopped a bombing with those same explosives at the federal currency exchange, also based on the city blueprints Mouse had looked up under orders from Donovan.

Halstead was both relieved and saddened by the success. On some level, he knew that it meant Mouse still trusted him and could be straight with him, at least to a point. But it also meant that Mouse had somehow gotten involved with some dangerous people and it was only a matter of time before it came back to bite him in the ass.

Of course, now that he knew his friend was alive, Halstead was going to do everything in his power to keep it that way.

After picking up a CI enrollment packet from Sergeant Platt at the front desk, Jay rushed back up to the Intelligence bullpen, taking the stairs two at a time. Detective Erin Lindsay met him at the top.

"You find him?" She asked, falling into step beside him easily. If there was one thing Halstead had learned about Voight's golden girl during his short time with Intelligence, it was that she often had the same gruff manner of speaking as her mentor.

Jay smirked, quirking an eyebrow at her. "Oh yeah, we got him. Mouse still in the box?"

"Yeah, but-"

"Thanks. I know he seems like a bit of a mess, but Mouse's actually-"

"Jay." The tone of Erin's voice stopped Halstead in his tracks. He didn't like the serious look in her eye. "Before you go in there, I want you to be prepared. I don't know who this guy is to you, but I don't think this was his first go round with Donovan's stash. He's been in full blown withdrawal for the past two hours."

Jay's expression hardened. Damn it, Mouse.

Erin continued. "Look, this might not be my place, but if you want to get him in a good program, I've got a few names."

Jay just nodded and walked away towards the interrogation room, though with less energy in his step. Gripping the door handle, he steeled himself for the confrontation to come.

Mouse jumped violently when Jay walked into the room, shutting the door behind him. If he had been fidgety before, he was now shifting back and forth in his seat, shaking visibly as his fists continuously clenched and unclenched by his sides. Focusing on Jay, Mouse cracked a smile.

"Hey, hey, Jay, my man," Mouse rattled off, almost looking like his old self before his expression took a serious turn. "You get him?"

"Yeah, Mouse," Jay couldn't help but smile slightly, looking down at the man he could barely recognize as his friend. "We got him."

Mouse actually laughed, sweat rolling down his face. "See, see, what'd I tell ya? And what'd you say, I help you, you help me, right?"

Jay nodded, sitting down at the table and flipping open the folder of paperwork. "Yeah, something like that."

"Somethin' like that," Mouse repeated, his eyes unfocusing slightly before locking back onto Jay. "So you, uh, you got somethin' for me?"

Coke. His friend was asking him to pay him back in coke. Jay snorted. "Yeah, I don't think so."

"Whaddaya mean?" Mouse lurched forward on the table, getting low and grabbing at Jay's forearm. "You said you'd help me out, man."

"I did," Jay agreed. "I said I'd help you out, not get you high. Look, I want to make you a confidential informant. We'll keep you out of our reports, protect you when you need it, and you get a cut of what you help us take off the street."

But Mouse didn't seem to be paying attention. He surged to his feet in a fit of nervous energy, but was shaking so much that he had to sit back down. "No, no, no, no, Jay, you gotta get me somethin', man. I'm crashin' here and-"

"Mouse, listen to me, you don't need the drugs." Jay tried to reason with him.

"What, like how you didn't need your bottle?" Mouse fired back, eyes wild.

Jay shot a glance at the one two way mirror, hoping that Lindsay wasn't out there watching. Was that was this was about? Some kind of trouble readjusting to civilian life, maybe full on PTSD? Jay had always thought Mouse had handled it all particularly well, but maybe that was just because he'd been too busy getting his own head straight.

"Please, man," Mouse pleaded, scrubbing at his hands violently with his grubby hands. "I can't sleep, keep seein' you burnin' up in that fuckin' humvee... But if I just stay awake, the coke helps me stay awake, Jay-"

It broke Jay's heart to see the former Ranger break down, the same man who had helped Jay through his own rough transition. Abandoning the paperwork, Jay reached across the table to grab Mouse by the forearms to still him and provide some kind of concrete anchor.

"Mouse - Greg. It's okay, man, I'm right here. Let me help you out."


	4. A Beautiful Friendship

The next couple of chapters will be slight AUs/add ons to actual CPD episodes. I'm not going to rewrite the entire episode (that would take so ridiculously long), just the few scenes that revolve around Mousetead friendship.

The episodes will be noted in the chapter titles.

Disclaimer: Still not my characters, just my wild ideas.

* * *

 _A searing pain jolted Halstead back to consciousness just as Mouse heaved him up and through a freshly broken window. As soon as Halstead's butt hit the sand Mouse was already moving, dragging the bigger man back and away from the burning humvee. It was all Jay could do to remain still and not fight his friend, the movement jostling his broken leg violently._

 _Three yards out from the humvee, Mouse paused, breathing heavily and letting out a rushed "Shit." Halstead felt the grip on his uniform release and heard several hurried slaps of gloves against fabric. A minute later, the gloved hand come back down hard on his shoulder and squeezed. "Halstead? You still with me?"_

"' _m here," Halstead ground out in response, gritting his teeth as the broken edges of bone grated together and his vision whited out momentarily. Vaguely, he thought he could hear another explosion erupt somewhere in the background._

 _He must not have been too far off, because Mouse suddenly jumped, bumping up against him and making him groan. "Sorry, man. Hang tight, we gotta get off this road."_

 _Then they were moving again, Mouse's fingers digging into the collar of his uniform and Halstead's useless leg bumping slightly over their sandy path. Halstead wasn't aware that they had reached the dip off the road until he heard Mouse's boots scrambling for purchase on the poorly packed sand and his friend grunt with the effort of hurriedly, yet carefully, lowering Halstead down._

 _Once down, Halstead found himself in a relatively shallow ditch. His head nearly poked out over the top and, keeping his back pressed against the dirt wall, he allowed himself to slouch down a little further into the sand. Next to him, Mouse was slumped over on all fours, breathing hard. Halstead focused in on a freshly charred patch on his friend's bicep. Mouse had been on fire._

 _Halstead flailed a hand towards him and though he didn't make actual contact, the movement succeeded in gaining Mouse's attention. "Mouse? You good?"_

 _Mouse lifted his head and, despite their situation and despite the gunfire they could hear back at the convoy, the comm specialist actually managed a grin. "There he is. How's your head?"_

 _If Halstead wasn't suddenly aware of an ache in his head that rivaled the pain in his leg, he might have noticed that Mouse had failed to answer his question. As it was, he could only sit blinking as Mouse scrambled to his knees to peer at the large gash in Halstead's skull._

" _It's killing me," Halstead admitted. With a cluck of his tongue at the look of the gash, Mouse ducked back down to look into Halstead's eyes. He held up a finger which Halstead followed obediently, or at least to the best of his ability._

" _Yeah, you've definitely got a concussion," Mouse concluded, shaking his head. "Idiot; should'a been wearin' your helmet."_

 _While Halstead's scrambled brain struggled for a retort, Mouse reached down and unclasped the standard issue M9 Beretta that had thankfully remained secure in Halstead's leg holster. Clicking the safety off, the comm specialist pressed it into Halstead's hands._

" _Ok, uh, you stay here. Shoot anything that doesn't look friendly, got it?"_

 _Then before Halstead could even protest or ask what the hell he was going on about, Mouse reached for his own handgun and scrambled back up over the lip of the ditch._

* * *

"So," Ruzek started causally, stuffing a French fry into his mouth. "How trustworthy is this CI of yours?"

Halstead didn't even hesitate. "Who, Mouse? He's good, man. Hasn't let me down so far."

That wasn't entirely true, Jay reflected as Mouse finally slid into the back seat, shivering dramatically and blowing on his hands as if that would distract Jay from the fact that they were shaking. Halstead took it all in: the shaking hands, the pale face and overly prominent cheek bones, the smudges of red beneath his eyes. The way that he seemed overly jittery, even by normal Mouse standards.

Mouse was using again.

Rehab had been one of Halstead's conditions. If Mouse made it through the mandatory 30 days at a rehab facility, Halstead would make sure he was enrolled as a CPD CI. Always better with a goal in mind, Mouse held up his end of the deal, stayed the full 30 days at the facility and actively participated in all his therapies. He was then back on the streets and even managed to stay clean for a whole two weeks before he fell off the wagon when Jay asked him to get close to a specific home security operator connected to a series of burglaries.

Jay couldn't exactly fault Mouse for slipping, not when he was the one responsible for putting his friend in that situation in the first place. Besides, Mouse assured him that he was only using every once and awhile, on "bad days," and never when he was "working." Jay didn't know how much of this he was supposed to believe, but Mouse actually seemed happy for the first time in a long time and he didn't want to push him away again.

"What's up, Halstead?" Mouse asked, interrupting Jay's thoughts.

"Hey."

Mouse shot a curious look at Ruzek. "Who's your friend?"

"Ruzek," Jay nodded his head in between the two. "Ruzek, Mouse."

Both men mumbled a low "What's up man?" and Mouse launched himself at the fries balancing on the center console between the two cops. Stuffing some of the warm fast food into his mouth, Mouse let out an appreciative "Thanks man."

Introductions taken care of, Halstead got straight to business. "Hey, listen, can you tell me anything about this construction site robbery in Harvey?"

Jay could've sworn that Mouse smirked at him. "Might be tapped in on that."

"Yeah?"

Mouse paused slightly and Jay knew what was coming. The CI looked between the two cops. "My ears, man, they get so waxy these days."

It was all Jay could do not to roll his eyes. He settled for shooting Ruzek an amused look. "Oh yeah, so waxy these days, his ears, yeah."

He pulled two folded $50s out of his jacket pocket and held them out in front of Mouse teasingly. When Mouse had first joined on as a CI, he'd been weird about taking money from Jay. Said he felt like he hadn't done enough to earn it. But after Jay brought the former Ranger some copies of the charges against the men he helped put away, Mouse's attitude changed completely, like he finally understood the true value of the information he was sharing.

Maybe he'd also come to realize that Jay didn't check in with his other CIs nearly as often as he did with Mouse, didn't bring the rest of them food or coffee or whatever. That sometimes it was less about stopping bad guys and more about checking in on a friend.

Today, Mouse was in top form and played his role excellently. He all but ripped the money out of Jay's hand, a smile taking over his face. "Yeah, ding ding! Clear as a bell, just like that!"

Ruzek laughed. "Just like that."

Mouse smirked, tucking the money into the back pocket of his jeans. "There's a lot of talk. There's this new player in town, he's, uh, lookin' for some bangers. I'm kind of serving as a… consultant."

That was exactly what Halstead had been hoping to hear. One thing that Jay had learned very quickly after making Mouse a CI was that Mouse was _very_ good at it. There was something about him, maybe his friendly nature, maybe the fact that he wasn't the most physically intimidating guy, that made it easy for people to trust him. Jay didn't need to wonder about it too much. Mouse had the same skills when he was in the Rangers, the ability to put people at ease, get close to them, and suddenly have access to all kinds of things he shouldn't have.

Hence the nickname.

Halstead exchanged a look with Ruzek, who was looking unabashedly impressed. "Can you get us a meeting? Tell him we're offering blasting caps and det cord."

Mouse's eyebrows went up. "What, straight up?"

Jay had never used Mouse for a face to face before, preferring to keep him as the silent go between, the unknown middle man. On some level he knew it was because he was trying to keep Mouse from getting in any deeper than he needed to, trying to keep him safe. But this was too good an opportunity to pass up.

"Yeah, straight up. All you're doing is organizing a meet."

Mouse only hesitated slightly, looking Jay directly in the eyes before shrugging his consent. After everything they'd been through, Mouse still trusted Jay without question. "Alright. Drive toward Erie and Sedgwick. I'll set it up."

* * *

And that was why Halstead had tried to avoid using Mouse for face to face meets up til now.

Charlie fucking Pugliese. That creepy, greasy looking guy he'd seen with Erin at the station now seemed to have his fingers in their case. Jay would have to talk to her before he brought Voight any kind of update. But that was only the second thing on his mind right now.

Charlie made Mouse. That meant Mouse was in danger.

More importantly, Charlie made Mouse because Jay had been too stupid to ask who exactly it was they were meeting before they walked into the building. It was a rookie mistake and not one he should have expected either Ruzek or Mouse to think of before hand. He was the more senior officer and Mouse was _his_ friend. That made Jay responsible.

"What the hell was that?" Ruzek demanded, throwing a glance back over his shoulder at the building they had just hurriedly exited.

"Just like he said, I met him with Lindsay." Halstead huffed, his mind working a mile a minute. He could feel Mouse pressing close to his back, the nervous energy running through the CI.

"I'm so made, man!" Mouse moaned, practically tripping over himself in the hurry to get away from the building.

Jay reached a hand back to steady and quiet him. "Relax, Mouse! I've got you on this one."

Despite his confident tone, Halstead didn't actually have a plan yet, just more of a goal: keep Mouse safe.

* * *

"Hey, Halstead," Mouse called, fingers curling around the wire mesh of the Intelligence holding cell. "I don't know if you remember, but, uh, I didn't do anything wrong. For once."

Halstead snorted a laugh, fishing for the keys in his pocket. "I know."

Mouse looked at him in exasperation. "Then why have I been sittin' in the cage all day, man?"

"It's called keeping your ass from getting killed," Jay quipped unlocking the cage door and motioning for Mouse to step out. "Or did _you_ forget that yesterday you walked two CPD officers in front of Charlie Pugliese? We might have him in custody, but I'm sure there are several of his contacts, _your_ contacts, who would be less than happy that you willing cooperated with the cops."

Mouse at least had the good grace to look chastised. "Fair point. So where to now, officer knight-in-shining-armor?"

Jay punched his friend in the shoulder, though he couldn't suppress a smile. "Keep it up, smartass, and I'll kill you myself. Come on."

Jay had a coffee waiting for Mouse in the car and for the most part, the rest of their ride was silent. But it was a comfortable silence, closer to the easy relationship that they use to have. Finally, Jay pulled to a stop in front of a dormitory-looking building with a big sign out front: St. Anthony's Community Home.

After taking in their surroundings, Mouse leveled Halstead with a questioning look. "Really, Halstead? We're doin' this again?"

"Yeah, we're doing this again," Jay replied, turning off the engine and giving his friend his full attention. "And we'll keep doing this until you get it right and get your life back together. You've got too much brain to waste on drugs and little tips, man."

Mouse nodded in understanding, though he couldn't resist one last quip. "I thought you found my little tips helpful."

"We do," Jay agreed, but he wasn't backing down. If this was going to work, if Mouse was going to do this right, he had to make the CI understand. "But this isn't the only life I want for you, Mouse. You can do so much more. You understand that, right?"

"If you say so." Mouse's voice was quiet, his gaze far away as he stared out into the darkness.

Halstead took that as a good enough sign that he was finally getting through to his friend. "So, this place is a little different. We've had several CIs stay here before. Okay, there's security and doctors and-"

"Shrinks," Mouse guessed.

"Yes, shrinks, and even a few nuns to keep you all in line." Jay chuckled, allowing himself to smirk a little. "I called ahead earlier and managed to grab you a room. You can stay here as long as you need. They've been briefed on your situation and they've already got a treatment plan to get you off the drugs."

Mouse nodded in acquiescence and Jay reached out to grab his shoulder. "Hey, look at me for a sec. For good this time, okay?"

Mouse looked him right in the eye and managed a small smile. "Yeah, Jay, okay. For good."

Satisfied, Jay released Mouse's shoulders and the two men sat in silence for a few minutes. Neither seemed to want to move, not the one who was going to be admitted nor the one who was trusting the staff to care for his friend. His _best_ friend, Jay amended silently to himself.

Because, when it came down to it, there was a pretty short list of people Jay would do anything for and Mouse was right at the top of that list.

"Mouse." Jay was just going to do it, to ask the question he'd been holding onto for the past year. For some reason it felt like now or never. "Why'd you leave, man?"

Mouse first looked startled, then his eyes went distant as he quieted. Jay couldn't seem to stop the words now that they were flowing. "I've been wracking my brain, trying to figure out why you walked out my door without a word. I mean, I know I wasn't always the easiest person to be around, but I at least thought-"

"Nah, man, it wasn't your fault." Mouse cut in, his pale blue eyes as serious and sincere as Jay had ever seen them. "It was… I, uh, I was circlin' the drain before you, you know, came home. And then you were back and you were losin' it and I was just barely keepin' it together, man, 'cause, 'cause you needed me to."

Jay swallowed hard, but couldn't bring himself to stop Mouse. It was about time they got this out in the open. Taking a breath, Mouse continued.

"I, uh, I kept screwin' things up. Took forever to find a job, with my record, and when I finally did, I lost it 'cause some guy made a stupid comment and I went off on him. But then you started turnin' things around and I was fallin' apart… I just couldn't do that you, couldn't drag you back down with me, you know?"

"Mouse," Jay said gruffly, his voice tight with emotion. "You didn't have to do that. I would've- I could've helped you, man."

Mouse ducked his head down in a shy nod. "I know, but I wasn't… wasn't thinkin' straight. I wasn't really sleepin', 'cause every time I closed my eyes… And that was when I ran into my friend Donnie from high school. He asked if I was still good with computers, said he had something that could take the edge off. I helped him out with a few, uh, consulting jobs before I realized what I was gettin' into."

"This Donnie have a last name?" Jay growled, his hand unintentionally straying to his sidearm.

Mouse, however, caught the motion and laughed quietly. "Easy, cowboy, he's already dead. Shot in the head the end of April. Guess he was givin' it to the wrong man's woman. Anyways, by then Eddie'd already introduced me to Donovan and I guess you know the rest."

Halstead shook his head, trying to take it all in. Sadly, it was the kind of story he'd heard so often in his career as a cop, but one that he'd never thought he'd have a starring role in. It touched him to know that Mouse had at least tried to keep it together, for him, just as much as it pained him to think that Mouse acted like he was bad for Jay, like his problems would rub off on the other man. Jay hadn't forgiven himself for not being there for his friend, not for a long shot, but he could only hope that he had finally started to make up for it.

With a sigh, Jay was finally the one who broke the silence. "Come on, man, I'll walk you inside."


	5. What Puts You on That Ledge

So sorry for the freakishly long wait! I kind of had a CPD writing block which I finally seem to have worked through.

I've made this chapter extra long to make up for my slowness in getting this up. This is a slight AU for 2x16 "What Puts You On That Ledge"

Thanks to everyone for the kind reviews and messages!

* * *

 _Stay awake, Halstead._

 _Jay lost track of how long Mouse had been gone. None of this felt real, not the burning sensation in his leg, the persistent throb in his head, the fact that he was huddled in a ditch in Afghanistan, alone. He could hear the 'pop, pop, pop,' of gunfire and smell the acidic smoke from the burning humvee, but it all seemed so far away._

 _Stay awake._

 _Mouse was right, he should have been wearing his helmet. But it was hot in this fucking desert and there was something in the back of his helmet that rubbed irritatingly against his scalp, leaving him with angry, raw patches of skin. He'd only taken it off for a second._

 _The sand over his head shifted suddenly, running down the dip and into his collar. Halstead tensed as the pounding in his head was replaced by the pounding of approaching footsteps. He gripped his Beretta tightly. Friendlies or enemies?_

" _Jay!"_

 _Mouse's call was barely a warning as four bodies suddenly came sliding down into the ditch with him in an explosion of sand. He swung the gun up and in their direction before catching sight of their dirty uniforms and weary faces. Mouse had returned with the men from the second humvee, Mackie, Garcia, and Hollinsworth._

" _Woah, easy soldier!" Mackie said, reaching out and giving Mouse a little shove. "You gave captain concussion a gun?"_

" _Damn right I did," Mouse defended. "What was he supposed to do if a hadji-"_

" _Alright, alright, enough." Hollinsworth barked, raising his hands to silence the bickering soldiers. "We don't have time for-"_

 _Pft! The sound of a bullet punching into the sand just behind Hollinsworth's head had the soldiers all sprawling forward on their stomachs, Jay included._

" _Shit," Mackie groaned from where Hollinsworth had gone down hard on top of him. "Where is he?"_

 _Garcia, one of the company's snipers and the only one who had managed to keep a hold of his rifle, poked his head up cautiously and peered through his scope. "Bastard's hiding behind our humvee."_

 _The next hour or so blurred together in Jay's mind. Garcia stood, rifle ready and resting on the sand, Hollinsworth acting as his spotter, taking the occasional shot at the two attackers who had dug in behind their humvee. Return fire was few and far between, but the men didn't want to move out while there were two hadjis out there waiting for them._

 _Jay faded out briefly, the pain in his head winning out over his resolve, only to fully regain consciousness to Garcia and Hollinsworth sinking gratefully into a sit, rubbing at their tired eyes. Mouse looked up from where he'd been slouched next to Halstead, fiddling with his radio._

" _Got 'em?"_

" _Fuckers are dead," Garcia spat in answer. All the same, the Rangers had a brief moment of silence. They were only killers because they were at war; none of them relished taking another person's life._

 _Mackie was the one to finally break the silence. "Now what?"_

 _The Rangers all exchanged a look before Hollinsworth took the lead. Normally, Jay was commanding officer, but with the current state of his brains questionable, the tactical decisions fell to Hollinsworth. "Now we gotta get word back to base, request an evac. Halstead needs a doctor and base should be informed that this road is mined. Mouse, how're comms lookin'?"_

 _Mouse sighed, dropping his radio in frustration. "No good. Mine's toast."_

" _We've got one of those old school, long range radios in the back of our truck," Garcia offered up._

 _Hollinsworth nodded in approval. "Okay, good. But for now, we need to move away from the road. One humvee's still burning and they're attracting too much attention. Mouse, you and Mackie move Halstead further down, Garcia and I will get the radio and meet back up with you."_

 _Like the well oiled unit they were, the Rangers all got to their assigned tasks. Hollinsworth and Garcia took off towards the humvees, guns at the ready, while Mackie and Mouse each arranged themselves under Halstead's armpits. On a count of three they had him up and moving forward down the gradual incline at a fairly good pace, considering that Halstead really wasn't able to help much. He did, however, manage to keep from passing out again._

" _Okay, Jay, we're gonna set you down." The threesome had made it about ten yards further down the slope and located a slight curve in the sandy wall that provided more cover than sitting out in the open. Maneuvering Jay into the curve, the two Rangers lowered Halsted down carefully._

 _Despite their care, the pain in Halstead's head spiked violently and he shoved Mouse back hurriedly before keeling over to the side and vomiting up the contents of his stomach. Unprepared, Mouse tripped backwards over his own feet._

 _It wasn't long before Jay reached dry heaves. Blinking past the tears in his eyes, he spat violently. "Ugh. Sorry, Mouse, I- Mouse?"_

 _Mouse stood off to the side, bent slightly at the waist. His face wore a pinched expression and had gone very white. But what really caught Jay's eye was the growing stain of red just above Mouse's hip as it spread down one leg of his fatigues._

" _What the hell is that?"_

* * *

Jay watched curiously as Ruzek and Atwater approached Voight, looking both sheepish and a tad nervous. The two younger policemen had been deep in conversation since they arrived that morning, psyching each other up. Jay could understand their apprehension. After Jin's murder, no one had been brave enough to suggest they bring in a replacement tech officer.

But an Intelligence unit without a techie was a seriously handicapped Intelligence unit and it was about time Voight did something about it.

"We're just not cut out for the high altitude stuff, boss."

 _Now or never, Halstead._ "Don't say another word. "I've got the perfect guy from the job."

With the tech position still open, Jay had been waiting for the right opportunity to bring up Mouse with Voight. With his skill and experience, Mouse might actually be overqualified for the position and, despite his frosty exterior, Voight was a bleeding heart when it came to second chances. The fact that the Sergeant had let Nadia stay on meant Mouse actually stood a chance.

"He did the explosives case with us last year. Mouse, you remember him?"

Voight fixed Halstead with a look that he normally reserved for their least cooperative suspects. "I remember everything, Jay."

"Alright." Jay kept his tone carefully light and resisted the urge to glance over at Lindsay; he was sure they would be talking about this later. "Then you'll recall that he did a great job for us. And when O gets here he'll tell you that to."

"I'm here." Olinsky called out, scooting his chair more out into the open. He nodded at Voight, talking around the straw in his mouth. "Yeah, he was solid."

"Yeah." Halstead gestured to Olinksy like he was an evidence display. "Plus, he's like a total tech whiz. And I would trust him with my life. In fact I have, many times."

Any further conversation was cut off as Commander Fisher and a lieutenant from Narcotics paraded into Voight's office. But the Sergeant's expression had shifted to something Halstead could consider more promising. "Bring him around."

"Alright." As soon as the door to Voight's office swung closed, Jay shot a look at Lindsay, which she returned pointedly. In another second she was up out of her seat, striding towards his desk.

"This Mouse the same Mouse we brought in-"

"The one and only," Jay cut her off hurriedly, wanting to squash the image of Mouse going through withdrawal in their interrogation room before it re-planted itself in her head. Lindsay didn't know the real Mouse, the Mouse who had joked his way through Ranger school and pulled Halstead back from the brink. Jay didn't want Lindsay thinking about his friend in the past tense.

Lindsay nodded thoughtfully, perching lightly on the edge of his desk and arching one eyebrow at him. "And you think that's a good idea?"

Jay couldn't help the sharp annoyance that flared in his gut. "I'll admit it, Mouse went through a rough patch. But he's getting through it and besides, everyone deserves a second chance. I thought you of all people would understand that."

Immediately Jay wished he could take it back, because Erin stood up abruptly, a brief look of hurt flashing in her eyes. Her arms came up to cross over her chest as though to form a protective barrier. "Okay, wow, tell me how you really feel."

There were a million things Jay wanted to say: how he hated sneaking around behind Voight's back when the Sergeant obviously knew what they were doing, how sometimes it was annoying that Lindsay acted like she was the only one in the unit with a hard-luck story. But this was neither the time or the place to have that conversation, so Jay pushed those feelings aside with a sigh. "Look, that was unnecessary and I'm sorry, okay? But this would be really good for Mouse, he would be a great fit, and I just don't want you to judge the guy before you've actually, really met him."

Lindsay looked at him searchingly, as if seeing something in him that she'd never noticed before. But then she cracked a slight smile and nodded. "Okay, fair enough."

* * *

Mouse arrived at the District around noon. Jay found him hovering just outside the back door like when he was a CI, selling tips for cash. Jay could only shake his head and smile; old habits die hard.

"Hey, Mouse." Jay reached out and clapped his friend's shoulder, thankful he had actually shown up. Ever since Halstead had pulled strings to get Mouse into St. Anthony's Community Home, the former Ranger had really been trying to turn things around. He attended all of his groups and therapies, followed the doctor's orders to ease off the cocaine, met Jay every couple of weeks just to check in. As of today, Mouse had been officially clean for almost six months.

And yet, in the back of his mind, Jay was always afraid his friend would slip up and walk out of his life again.

"Halstead." Mouse greeted Jay with one of his awkward little chin tilts, rocking back and forth on his heels nervously. "So, uh, I know your message said somethin' about a job, but I didn't have slacks or anythin', so…"

Mouse trailed off in embarrassment, glancing down at his clothes. He wore a plaid button up under a thin, navy sweater that looked clean but well worn around the neck and seams. His black jeans were starting to fade around the knees, but Jay could see that Mouse had gone to the effort of cleaning up his old boots as much as possible. He gave his friend a reassuring nod.

"You look fine," Jay replied, gesturing for Mouse to follow him into the District. "Besides, once Voight sees what you can do with a computer he won't care if you come to work wearing a dress."

Halstead barely got Mouse up the stairs and into the Intelligence bullpen before Ruzek and Atwater grabbed him. They quickly settled him at Atwater's desk, yammering about this and that software that he would be expected to learn as their new tech. Mouse listened politely, nodding when necessary as he tapped away on the keyboard, exploring their underutilized computer system. Finally, the youngest members of Intelligence seemed to run out of things to say and they fell silent, watching Mouse closely like he was performing a magic trick.

After a minute of silent typing, Mouse gestured at the two officers. "So, what, you guys were in charge of the tech before?"

Towering over the file cabinet he was leaning against, Atwater nodded. "Yeah, that's right."

If he was skeptical about their abilities, Mouse was a good enough actor to keep it to himself. "Let me ask you, you got like a Cat 5 or a fiber wire, or-"

Ruzek looked confused and Atwater coughed lightly, cutting him off. "Uh, what do you think?"

Jay snorted a laugh as Mouse just smiled placatingly and threw up a thumbs up. "I'll figure it out."

"So, wait, you were in the Ranges with Jay, right?" Ruzek asked, drawing on the little information they'd been able to get out of Jay about their new techie.

Mouse shot a smirk in Jay's direction and nodded. "You know, I could tell you some stories about this guy."

"Yeah, but he won't though." Jay said, giving Mouse a wide, yet warning smile. He made a mental note to talk with his friend about work boundaries when Voight strolled into the room, holding Mouse's CI file. Halstead braced himself; this was going to be the hard part. "Hey, Sarge, this is the guy I was telling you about. This is Greg Gerwitz, aka Mouse."

Mouse looked slightly apprehensive as Voight stopped right in front of the desk where he was sitting, but managed to cover it up with his signature, self-deprecating humor. "Sir, it's a silly nickname, but I'm the first to admit it."

Voight hummed thoughtfully and then jumped right into the tough questions. He glanced between the file in his hands and Mouse's face. "What's this about a truck load of BlueRay players last year?"

Mouse's eyes flickered towards Jay as he fumbled for an answer. "See that case was actually- that, that was expunged. I was tryna-"

Halstead almost flinched guiltily. That arrest had been on one of Mouse's last jobs as his CI. Halstead had asked Mouse to get in with a crew of robbers with serious taste in new tech. According to the deal he'd struck with the DA's office, the case should have been expunged. Apparently he had some ball yanking to do after shift.

But that wasn't the worst of it. An incredulous look came over Voight's face. "Then busted for hacking a DOD comm satellite in '09?"

Ah, yes, the infamous DOD hack that had gotten Mouse pulled straight out of basic training and thrust into Halstead's class at Ranger School. From what Halstead understood, Mouse had hacked the satellite partially out of boredom, partially because some of his fellow Army cadets dared him to try. On one hand, it was a serious crime. On the other, it was a clear indicator of Mouse's crazy skills with computers.

Mouse had the grace to look chastised, his gaze sliding away from Voight's and down to the desktop in front of him. "For that I take full responsibility."

"Sarge," Halstead jumped in, hoping to turn the conversation in Mouse's favor. "I know he doesn't look great on paper. Just wait 'til you see what he can do."

Before Voight could answer, Mouse made a few definitive strokes on the keyboard and cleared his throat. "Excuse me, Sergeant Voight, sir? Would, would you mind taking a look at your cell phone?"

Voight looked a second away from exasperation. "My phone?"

"Yessir."

Voight looked to Halstead for some explanation, but the detective could do no more than shrug. He had a general idea of what Mouse might try to do, but figured it was better to keep his mouth shut and let his friend's skills do the talking. Voight finally gave in, pulling his phone out of his pocket and thumbing it on. He blinked at it shortly before tilting the screen towards Halstead, who saw the Sergeant's formerly plain wallpaper had been replaced with a picture of Mouse.

"Cute."

"See, I was able to crack that in about two seconds," Mouse said humbly, leaning back a bit in the desk chair. "Imagine what a hacker could do with a day."

Voight looked down at his phone again and Halstead could see it, a slight hint that the older man was actually impressed by what Mouse could do. When Voight glanced up, he found all of his officers staring at him expectantly and shrugged. "It's fine with me, but Platt has to sign off too."

"Yes!" Ruzek jumped to his feet excitedly and smacked Mouse on the shoulder in congratulations. Before Halstead could say anything, Lindsay came striding towards them, hanging up her phone. Voight looked at her eagerly.

"Where are we at?"

"Alright, so the lab's on board, but it's too late to switch out the drugs." Lindsay informed them. "Narcotics is going to wait in the shadows. They'll tail the crew, ID the stash house, then sit tight until we know Antonio's okay and we give them the green light."

Voight nodded in satisfaction, already heading out. "Let's roll out in 20 minutes."

As Atwater and Ruzek headed to the locker room for their vests, Halstead and Lindsay exchanged a look. It was long, slightly tense - this case was turning out to be a lot more stressful than they had expected - and full of something Jay couldn't quite put his finger on. Longing? Regret? Whatever it was, Lindsay was the first one to break eye contact, striding towards her desk without so much as a glance at Mouse.

For his part, Mouse didn't seemed phased by her dismissal. Instead he threw a full smile Jay's way that the detective couldn't help but return. "See, man, what'd I tell you?"

* * *

Jay wandered into the tech room where Nadia had told him he'd find Mouse. Sure enough, the former Ranger was already seated in front of Jin's double monitors, typing rapidly and moving quickly from screen to screen. No matter how many times Jay saw Mouse at work, he never got any better at deciphering what exactly his friend was doing.

He whistled slightly, drawing Mouse's attention to him. "Hey, getting settled in?"

Mouse glanced back at him and raised one hand. "Yeah. Give me a sec."

Halstead leaned against the thick counter, listening to the gentle whizz of the printer as Mouse printed whatever it was he was working on. "So I'm assuming it went well with Platt?"

"Yeah, uh, yeah it did," Mouse replied, springing from the chair to attach a sticky note to the back of his printout. "I almost blew it when she asked about my medical discharge, but, uh, she kinda cut me some slack."

Jay frowned slightly at that. Even he didn't know the truth about Mouse's medical discharge. He'd tried to look into it back when Mouse went missing, but he hadn't been able to convince anyone at the local VA to hand over Mouse's records. 'Course, he wasn't a detective for nothing. Seeing as Mouse didn't have any lingering physical injuries, he'd come to assume the medical discharge was for more psychological reasons. PTSD, perhaps.

Not that he'd ever gotten up the courage to actually ask Mouse.

"Yeah? You okay?"

Mouse responded with the kind of smile Halstead hadn't seen his friend wear in a long time, a smile that reached his eyes and emphasized his dimples. But before Mouse could actually say anything, Voight came in looking tense. Mouse snapped to attention. "Sergeant."

Voight approached the counter beside Halstead. "Any word on Antonio?"

Mouse shook his head. "No, not yet, sir."

"Alright, we've got a designated landline that he knows. It rings, you call me," Voight ordered, already moving back towards the door.

"Will do. Oh," Mouse called, scrambling to bring forward the printout he'd made. "I did get a lead on the woman seen leaving the Argyle hotel with Manning. Yeah, I pulled an image from an ATM cam across the street from the hotel. The ID came back as Amber Banks. Now, state tax returns confirm that she waits tables at the Tortoise Club which is, uh, Vince Parker's restaurant. I attached the home address on the back."

Studying the woman in the printed photo carefully, Voight flipped it over to read the small, yellow sticky that noted Amber Bank's address in Mouse's hurried scrawl. This time the Sergeant looked openly impressed. "Nice pull."

Voight regarded Halstead as he headed out the door. "Interesting cat, Mouse."

* * *

It was finally over. Antonio was back safe, the bad guys were behind bars and Narcotics' undercover… well, he was their problem now.

Halstead was reclining in an extra desk chair that he had pulled into Mouse's new tech den, nursing a beer as he watched Mouse fiddle with something under a light and magnifying glass. The smaller man sighed happily, unable to wipe that stupid grin off his face.

"Roll call, chain of command? It's almost like being back in fatigues, you know?" Mouse let out a quiet laugh. "Didn't think I'd miss it, but I do. I like the structure. Yeah, I need this."

"Don't screw it up," Halstead said bluntly. Even as he spoke he was aware that, without Mouse's intel today, they probably wouldn't have found Antonio on time. He just hoped Mouse recognized how much good he could do here, working with Intelligence.

"I won't," Mouse announced happily before turning to fix Jay with a more serious stare. "Hey, I want to let you know that I really appreciate you doin' this for me."

Looking back at his friend, Halstead didn't really know what to say. They'd been through so much together. "You were there for me, right?"

"Yeah." Mouse's smile turned slightly sad and he stood to grab his beer from the computer console. "You know what's crazy? You and I went through the exact same thing that day and uh, I've been, I've been bouncin' around ever since and you've got the world by the tail."

Jay wanted to reach out and shake self-directed negativity right out of his friend. The only reason he'd managed to pull himself together at all was because Mouse had refused to give up on him, had put up with his shit even when the smaller man had been falling apart himself. Besides, Halstead still sometimes felt the darkness hovering there, waiting to descend on him.

"Don't be so sure."

Mouse nodded vaguely, sipping at his beer thoughtfully. Then he gave himself a little shake and the shadows seemed to fall away from him ever so slightly. "So, what's goin' on? You seein' somebody?"

"I guess I was, for a minute." Halstead said, the words tasting bitter in his mouth. He was glad that he and Erin had finally talked, but needless to say wasn't exactly happy with the outcome. She was his partner in every sense of the word and he wished that their timing and circumstances were different.

But Jay didn't want to talk about Lindsay, so he cleared his throat and changed the subject yet again. "So, how's St. Anthony's working out?"

"Uh," Mouse hesitated, taking another swig of his beer. "It was, uh, it was good for what is was. But I'm actually, uh, I'm lookin' for a place."

Halstead frowned. He knew for a fact that Mouse didn't have the kind of money to be 'lookin' for a place.' "Oh yeah? What's that about?"

Mouse looked down at his shoes sheepishly, then out at the door to the tech room, anywhere but at Jay. "It wasn't exactly my idea. The, uh, director decided it might be better for me to live on my own."

"He did what?" Jay could feel his temper starting to boil. The whole point of the group home was to give people who weren't ready to be on their own a safe place to stay. "Did he say why?"

"Yeah, uh, apparently," Mouse seemed to shrink in on himself slightly, but he couldn't deny Jay the truth. "Apparently my nightmares are freakin' the other residents out. But, it's cool, see, 'cause I'm only havin' them now I'm clean…"

Jay's heart dropped at the ashamed look on Mouse's face. No veteran should ever be made to feel that way, especially one who'd had as hard a time as Mouse. Jay himself still suffered through the occasional nightmare, normally about the day of the convey incident or the young female suicide bomber. If this jackhole of a community home director had seen even a fraction of what Jay and Mouse had lived through… Well, Jay had a few choice words he'd like to have with the man.

But Mouse looked uncomfortable enough, so Jay merely growled a laugh, the best he could do under the circumstances. "What a dick. Well, forget him. You can come and stay with me."

Mouse looked up at him gratefully, but still seemed skeptical. "Jay, that's not what I-"

"No, seriously, man, it's cool," Jay assured him. "I've actually really missed having you around. Besides, I moved since last time, so you can even have a real bed. No couch sleeping necessary."

Mouse was watching him closely with a look of wonder on his face like he couldn't decide what he'd ever done to deserve a friend like Jay. Funny, 'cause Jay was thinking exactly the same thing.

"Really? You sure you don't mind?"

Jay smiled, his first genuine smile in days. "It's about time you came home, don't you think?"


End file.
